1. Field of the Invention
This invention in general relates to variable focus lenses and in particular to an elastomeric variable focus lens element which can have its focus continuously changed over a predetermined range in response to a variable tensile stress uniformly applied around the peripheral edges of the element.
2. Description of the Prior Art
Several types of variable focus lens systems are well-known in the optical arts. The type most commonly found in practice is perhaps the multi-element glass lens that is optically structured so that its focus can be continuously varied by changing the axial air spacing between its elements through the use of movable mechanical lens mounts.
Another type of variable focus lens system utilizes a pair of optical refracting plates having surfaces which are specially configured to in combination continuously define spherical lenses having different focal lengths as the plates are displaced with respect to one another transverse to their respective optical axis. As an example of this type lens, reference may be had to U.S. Pat. No. 3,305,294 issued to L. W. Alvarez on Feb. 21, 1967 and entitled "Two-Element Variable-Power Spherical Lens" or to U.S. Pat. No. 3,583,790 issued to James G. Baker on June 8, 1971 and entitled "Variable Power, Analytic Function, Optical Component In The Form Of A Pair Of Laterally Adjustable Plates Having Shaped Surfaces, And Optical Systems Including Such Components". Such refracting plate systems as is well-known may be used separately or in combination with other components to effect optical power changes for purposes of focusing and, as indicated in the Baker patent, supra, can also be favorably corrected for aberrations.
Another known variable focus lens is the fluid or gas type. In this type, flexible transparent membranes or plates generally are mounted in a support housing to define one or more chambers which can be selectively filled with a fluid, gas or jelly having a suitable index of refraction. The pressure or volume of the contents of each chamber can be adjusted so that the membranes or plates deform in a predictable manner while the fluid assumes the interior shape of the chamber to define a lens. In the case where more than one chamber is utilized, it is possible to correct for spherical and chromatic aberrations. Examples of fluid lenses are shown and described in U.S. Pat. No. 2,300,251 issued to E. F. Flint on Oct. 27, 1942 and entitled "Variable Focus Lens" and U.S. Pat. No. 3,161,718 issued to W. V. DeLuca on Dec. 15, 1964 and entitled "Variable Power Fluid Lens".
It is obvious that the variable focus lens is of fundamental importance in the practice of the optical arts as is evidenced by the various types which have been devised by those skilled in the art and discussed above. Equally apparen is the fact that each type of variable focus lens has advantages and disadvantages depending on the particular application. The fluid type lenses, for example, can be made quite large and can result in considerable savings in weight and space compared with a comparable glass system.
Because the variable focus lens is of such fundamental importance, it is a primary object of the present invention to provide an elastomeric type variable focus lens for use in the optical arts.
Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the apparatus possessing the construction, combination of elements, and arrangement of parts which are exemplified in the following detailed disclosure.